The present invention relates to a remote meter reading apparatus comprising an interphone system for voice communication.
Due to the high personnel costs for manually reading utility meters such as for electricity, gas, water and the like, systems have been developed to read the meters by remote control from a main station. The meters have typically been linked to the main station via radio and telephone communications.
However, it has been determined advantageous to provide a separate transmission line for reading the meters. In order to ensure proper operation of the system, a diode must be provided in the transmission line to block reverse current flow from the main station to the meters.
It is often necessary for maintenance personnel to communicate the results of repair operations on the meters to the main station, preferably as soon as the operations are completed. The most advantageous method of providing this communication is by interphones disposed at the meters and main station which are connected together through the same transmission line used to read the meters. The maintenance personnel carries an interphone handset for connection to the transmission line at the maintenance location and a similar interphone handset would be permanently connected to the transmission line at the main station.
However, such an interphone system has been heretofore impossible since the reverse blocking diode serves to half wave rectify the audio interphone signals. Such half wave rectified signals are unintelligible.